This invention relates to a method of and apparatus for producing power, and more particularly, to a method of and apparatus for producing uninterruptible power for communication systems such as communication systems that are also located in urban areas or in the vicinity of towns and also only stand alone systems.
In systems provided for providing uninterruptible power particularly for communication systems several options have been available: photovoltaic systems, thermoelectric generators (TEG) or organic Rankine cycle energy converters (OEC). In addition, uninterruptible power sources (UPS) for short time periods as well as UPS""s and diesel generators for long time use or diesel generators and a flywheel system.
In photovoltaic systems, batteries are used to compensate for the hours/days without solar radiation. Usually, the batteries are very large and, in most cases, the choice is for Nickel-Cadmium batteries. The reason is that the photovoltaic systems require batteries to work on deep discharge cycles, for which the Ni-Cad batteries are much better adapted than Lead Acid batteries. The problems arexe2x80x94very high cost for batteries and the need for maintenance of the batteries. In any case, in a 20-year project, the Ni-Cad batteries have to be replaced at least once. In telecommunication systems powered by photovoltaic cells need always batteries.
As far as thermoelectric generators (TEG) are concerned, since telecommunication equipment operates at varying load, and the TEG are continuously delivering full rated power, batteries are necessary for correcting the supply of power to the equipment. Moreover, the TEG requires use of dummy loads for dissipating the surplus of power delivered and not used by the telecommunications equipment. As TEG cannot trickle charge the batteries, additional battery chargers are required. If not, the battery will not be properly charged, and will require additional maintenance and manual charging during maintenance and the lifetime will decrease. The telecommunication systems powered by TEG always need batteries.
Turning to organic Rankine cycle energy converters (OEC), since they operate at varying load, they can trickle charge the batteries and thus increase their lifetime. In telecommunication systems, the OECs can be used in hot standby configuration. If one OEC fails, the second will deliver the full station load. The transient period until the second OEC will deliver the full load is of a few minutes (up to about 20-50 minutes) and could be reduced by either adding a very small standard battery to OECs to deliver a few AH during the transient period.
In a related system disclosed in U.S. Pat. No. 4,982,589, the disclosure of which is hereby incorporated by reference, a hybrid power plant is disclosed that includes an intermittently operable non-fuel consuming power generator, such as a photovoltaic cell array, or a wind generator, connected through a control-circuit to a battery for changing the same and for supplying current to a time-wise, substantially constant, electrical load. In addition, this hybrid power plant includes an electric generator connected to an intermittently operable prime mover, such as a Rankine cycle organic vapor turbogenerator, for charging the battery and supplying current to the electrical load when the prime mover is operated, and a sensor for sensing at least one electrical parameter of the power plant. With such an arrangement, the prime mover is operable only when the power generator is not operating.
Batteries are used in all the telecommunication projects to provide DC power to the telecom equipment and the reliability and availability of the system depends strongly on the battery characteristics.
The batteries have a limited lifetime and if not properly charged and maintained they have to be replaced a few times during the life of a project estimated as 20-25 years.
In addition, the battery condition cannot be correctly assessed, and it will normally fail without any kind of advance notice, thus causing shut down of the stations. Moreover, the battery fails when they are actually needed so that, when there is an electric grid power outage, the diesel generator fails when it is attempted to start it consequently causing the battery, UPS and diesel generator not to provide power.
It is therefore an object of the present invention to provide a new and improved method of and apparatus for providing uninterruptible power wherein the disadvantages as outlined are reduced or substantially overcome.
Apparatus for producing uninterruptible power according to the present invention comprises a hot standby organic Rankine cycle turbine system. No batteries are needed in the present invention. In one embodiment of the present invention apparatus for producing uninterruptible power according to the present invention includes a high-speed flywheel; and a single hot standby organic Rankine cycle turbine system. In another embodiment of the present invention apparatus for producing uninterruptible power according to the present invention includes two hot standby organic Rankine cycle turbine systems operating in parallel. In this embodiment both hot standby organic Rankine cycle turbine systems include a sonic nozzle for ensuring that the pressure in the boiler of the hot standby organic Rankine cycle turbine system operates at relatively high pressure. Furthermore in this embodiment one hot standby organic Rankine cycle turbine system includes a control valve for opening and closing in accordance with the output of the generator of the other hot standby organic Rankine cycle turbine system. In addition, here the other hot standby organic Rankine cycle turbine system also includes a control valve for opening and closing in accordance with the output of the generator of the other hot standby organic Rankine cycle turbine system. In this embodiment, the relatively high pressure of the boiler is suitable for producing full power output from the organic Rankine cycle turbine included in said hot standby organic Rankine cycle turbine system.
Furthermore in the embodiment of the present invention including a high-speed flywheel a motor is included for rotating the turbine when electric power is available from the electric grid. This embodiment also includes a heater comprising a burner for combusting fuel. In addition, the present embodiment includes an electric heater for heating to liquid organic working fluid when electric power is available from the electric grid. Moreover, in the present embodiment a three-way valve is included for supplying, when electric power is available from the electric grid, sufficient organic working fluid vapor for operation of the turbine bearings only.
In addition, the present invention includes a method for producing uninterruptible power and comprises the step of providing a hot standby organic Rankine cycle turbine system for producing uninterruptible power. In one embodiment of the method for producing uninterruptible power a high-speed flywheel is provided; and a hot standby organic Rankine cycle turbine system that produces power is provided. In a further embodiment of the method for producing uninterruptible power by providing a hot standby organic Rankine cycle turbine system two hot standby organic Rankine cycle turbine systems operating in parallel are provided. In this embodiment, relatively high pressure is maintained in the boiler of the hot standby organic Rankine cycle turbine system by using a sonic nozzle for supplying organic working fluid vapor to the organic turbine. Furthermore, in the present embodiment, a control valve is provided for supplying further working fluid vapor from the boiler to the organic turbine in response to a signal from the output of the generator of the other hot standby turbine when the output falls below a certain threshold such that the output of the first hot standby organic Rankine cycle turbine is substantially full power. In addition, in this embodiment relatively high pressure is maintained in the boiler of the other hot standby organic Rankine cycle turbine system by also using a sonic nozzle for supplying organic working fluid vapor-to the organic turbine of the other hot standby organic Rankine cycle turbine system. Moreover, in the present embodiment a control valve is provided for supplying further working fluid vapor from the boiler to the organic turbine contained in the other hot standby organic Rankine cycle turbine system in response to a signal from the output of the generator of the first hot standby turbine when the output falls below a certain threshold such that the output of the other hot standby organic Rankine cycle turbine is substantially full power. Additionally, in this embodiment, the relatively high pressure maintained in the boiler of the hot standby organic Rankine cycle turbine system is such that the relatively high pressure of the boiler is suitable for producing full power output from the organic Rankine cycle turbine included in said hot standby organic Rankine cycle turbine system.
Furthermore, in the embodiment of the method for producing uninterruptible power in which a high-speed flywheel; and a hot standby organic Rankine cycle turbine system that produces power are provided, an electric motor is operated for rotating the turbine when electric power is available from the electric grid. In this embodiment, sufficient organic working fluid vapor is supplied to the condenser for supplying organic working fluid condensate only to the bearings of the turbine when electric power is available from the electric grid. In addition, in the present embodiment, an electric heater is operated when electric power is available from the electric grid that heats the organic working fluid liquid present in a boiler such that sufficient organic working fluid vapor is produced for supplying organic working fluid condensate from the condenser only to the bearings of the turbine. Furthermore, in this embodiment, power is supplied to the electric grid using the high-speed flywheel when electric power is not available from the power grid. Moreover, in accordance with the present embodiment, organic working fluid vapor is supplied only to the nozzles of the turbine and the turbine is rotated using heat stored in the heated working fluid present in the boiler of the hot standby organic Rankine cycle turbine system when electric power is not available from the power grid. In addition, a burner for heating the organic working fluid liquid present in said boiler is switched on when electric power is not available from the power grid. Additionally, the electric heater is switched off when electric power is not available from the power grid.